Re: [GHC] #14315: GHC panic caused by destructuring with qualified name

4 Oct 2017

      #14315: GHC panic caused by destructuring with qualified name
-------------------------------------+-------------------------------------
        Reporter:  bloxx             |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.2.1
      Resolution:                    |             Keywords:
Operating System:  Linux             |         Architecture:  Other
 Type of failure:  Compile-time      |            Test Case:
  crash or panic                     |
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by bloxx):

 * architecture:  Unknown/Multiple => Other

Old description:
...
I have a cabal project with the following files:
{{{#!hs
-- src/Alt.hs
module Alt where
data Pizza = Pizza { filling :: String }
-- ===========
-- src/Main.hs
module Main where
import qualified Alt as A
data Pizza = Pizza { filling :: String }
unpizza :: A.Pizza -> String
-- to fix it, replace "filling" with "A.filling"
unpizza A.Pizza { filling = filling } = filling
main :: IO ()
main = putStrLn "Hello Haskell!"
}}}
Of course, this is not valid code. "filling" belongs to "Pizza" and
"A.filling" belongs to "A.Pizza". But it causes a panic in GHC 8.2.1
instead of an error, so I suppose it is a bug. Can you reproduce this
behavior?
New description:

 I have a cabal project with the following files:
 {{{#!hs
 -- src/Alt.hs
 module Alt where

 data Pizza = Pizza { filling :: String }

 -- ===========
 -- src/Main.hs
 module Main where

 import qualified Alt as A

 data Pizza = Pizza { filling :: String }

 unpizza :: A.Pizza -> String
 -- to fix it, replace "filling" with "A.filling"
 unpizza A.Pizza { filling = filling } = filling

 main :: IO ()
 main = putStrLn "Hello Haskell!"
 }}}

 Of course, this is not valid code. "filling" belongs to "Pizza" and
 "A.filling" belongs to "A.Pizza". But it causes a panic in GHC 8.2.1
 instead of an error, so I suppose it is a bug. Can you reproduce this
 behavior?

 Edit: GHC tells me:

 <no location info>: error:
     ghc: panic! (the 'impossible' happened)
   (GHC version 8.2.1 for x86_64-unknown-linux):
         translateConPatVec: lookup

--

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14315#comment:2
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler